Reductive alkylation reactions using modified nickel catalyst systems

ABSTRACT

N-ALKYL SUBSTITUTED AMINES ARE PRODUCED BY REACTING AMINE COMPOUNDS, NITRO COMPOUNDS OR NITROSO COMPOUNDS WITH AN ALDEHYDE OR A KETONE IN THE PRESENCE OF HYDROGEN AND A CATALYTIC AMOUNT OF A TWO COMPONENT OR A THREE COMPONENT CATALYST SYSTEM, THE FORMER COMPRISING A NICKEL CATALYST AND AN ACID, AND THE LATTER COMPRISING A NICKEL CATALYST, AN ACID AND SULFUR-CONTAINING COMPOUNDS.

United States Patent REDUCTIVE ALKYLATION REACTIONS USING MODIFIED NICKEL CATALYST SYSTEMS Farris H. Wilson, Jr., Cuyahoga Falls, Ohio, assignor to The Goodyear Tire & Rubber Company, Akron Ohio No Drawing. Continuation of application Ser. No.

606,010, Dec. 30, 1966. This application Dec. 3,

1969, Ser. No. 876,174

Int. Cl. C07f 85/08 US. Cl. 260-576 9 Claims ABSTRACT OF THE DISCLOSURE N-alkyl substituted amines are produced by reacting amine compounds, nitro compounds or nitroso compounds with an aldehyde or a ketone in the presence of hydrogen and a catalytic amount of a two component or a three component catalyst system, the former comprising a nickel catalyst and an acid, and the latter comprising a nickel catalyst, an acid and sulfur-containing compounds.

This is a continuation of application Ser. No. 606,010, filed Dec. 30, 1966.

This invention relates to new and highly effective catalytic systems and to processes in which they may be used. More particularly the invention relates to improved catalytic systems that are useful in reductive alkylation reactions.

Reductive alkylation reactions such as take place between an amine, a nitro or a nitroso compound when reacted with an aldehyde or ketone in the presence of hydrogen are commonly employed to produce N-alkyl substituted amines. Such reductive alkylation reactions are known to be catalyzed by certain metallic catalysts. However, many of the previously known metallic catalysts that are reasonably effective in promoting reductive alkylation reactions also have a tendency to promote one or more undesirable side reactions. For example, reductive alkylation reactions employing an amine, hydrogen and an aldehyde or ketone frequently result in the reduction of a substantial portion of the aldehyde or ketone to the corresponding alcohol. Another undesirable competing reaction when the nitro, nitroso or amine employed is an aryl compound is the reduction of the aromatic ring.

US. Pat. No. 3,366,684, issued J an. 30, 1968, discloses improved and highly effective catalytic systems for reductive alkylation reactions. This catalytic system comprises a nickel catalyst in combination with free sulfur or sulfur-containing compounds. The use of sulfur or sulfur-containing compounds along with the nickel alkylation catalyst is shown to increase the yields obtained in reductive alkylation reactions without promoting undesirable side reactions.

It is an object of this invention to provide other improved and highly effective catalytic systems for reductive alkylation reactions. fit is a broad object of this invention to provide reductive alkylation catalytic systems which will produce high yields of the desired N-alkyl substituted amine. It is a specific object of this invention to provide a reductive alkylation catalyst that will produce a high yield of the desired N-alkyl substituted amine without promoting undesirable side reactions and in particular the reduction of the aldehyde or ketone alkylating agent to the corresponding alcohol. It is a still further object of this invention to provide an improved process for producing a high yield of N-alkyl substituted amines.

In accordance with the present invention some of the above objects are accomplished by using a two-component catalytic system while other objects are accomplished by using a three-component catalytic system to effectively reductively alkylate nitro, nitroso or amine compounds.

The two-component system comprises concentrated metallic nickel or nickel dispersed on an inert carrier material and an acid containing no sulfur (i.e., sulfur-free acids) and sulfur-containing acids in which the sulfur is in the form of a radical. The three-component system comprises the twocomponent system and a modifier comprising free sulfur or sulfur-containing compounds which contain at least a portion of said sulfur in the form of a -S- and/or a radical.

Nickel catalysts broadly may be used in accordance with the present invention to produce improved catalytic compositions. The term nickel catalyst as employed throughout this specification and in the accompanying claims includes the following materials:

(1) relatively pure metallic nickel that may be in finely subdivided form;

(2) metallic nickel further modified with small amounts of other metals such as cobalt, chromium and zirconium; and

(3) metallic nickel in pure form or modified with small amounts of other metals supported on an inert carrier such as kieselguhr, charcoal, clays, alumina, etc.

Examples of suitable sulfur-free acids and sulfur-containing acids in which the sulfur is in the form of a (1) mercaptans (2) sulfenyl thiocyanates (3) sulfenamides (4) sulfenic esters (5) sulfenic anhydrides (6) thiophosphites (7) thiophosphates (8) thio ortho esters (9) alkyl thio sulfates (10) thio sulfonic esters (11) thio sulfinic esters (12) thio sulfite esters (13) hydroxy mercaptans (14) alkoxy mercaptans (15 cyano mercaptans (16) aldehyde mercaptans (17) keto mercaptans (18) sulfide mercaptans (19) amino mercaptans mercapto acids organic sulfides inorganic sulfides hydroxy disulfides amino disulfides aldehyde sulfides keto sulfides thio amines cyano sulfides heterocyclic compounds containing ring sulfur thiones sulfide acids disulfide acids mercaptals mercaptoles disulfides polysulfides thio acids thiol esters thion esters thio anhydrides dithio acids thio amides thiol carbonic esters thion carbonic esters dithio carbonic esters dithiol carbonic esters dithiol carbonic salts trithio carbonic esters trithio carbonic salts thiol carbamic esters thion carbamic esters dithio carbamic acid esters thiol carbazates thiuram monosulfides thiuram disulfides thiuram polysulfides thioureas isothiuronium salts thiols thio semicarbazide thio carbazone sulfur halides sulfoxides sulfide acid esters addition to the above classes of compounds that may be effectively employed as sulfur-containing modi' fiers in the practice of this invention, any compounds containing a multiplicity of any of the above characteristic groupings may also be employed.

The preferred sulfur-containing modifiers include sulfur and the following classes of sulfur-containing compounds selected from the classes enumerated above.

thioureas sulfide acids mercapto acids thio amides disul'fide acids thiuram disulfides mercaptans of heterocyclics containing ring sulfur disulfides of heterocyclics containing ring sulfur heterocyclics containing ring sulfur cyano sulfides sulfoxides thio acids organic sulfides mercaptans dithio acids sulfides of heterocyclics containing ring sulfur sulfide acid esters The most preferred modifiers that may be employed in accordance with the present invention are those compounds which when employed with a nickel catalyst and an acid according to this invention produce a catalytic system that is effective in catalyzing a reductive alkylation reaction to provide at least a percent yield of the desired N-alkyl substituted amine compounds. These most preferred modifiers include sulfur and the following classes of sulfur-containing compounds.

sulfide acids thiuram disulfides cyano sulfides sulfoxides organic sulfides mercaptans of heterocyclics containing ring sulfur sulfides of heterocyclics containing ring sulfur heterocyclics containing ring sulfur The most highly preferred three-component catalytic system is comprised of a nickel catalyst, thiodipropionic acid and toluene sulfonic acid. The three-component system is preferred in general over the two-component system.

Any of the aldehydes and ketones that are normally employed in a conventional reductive alkylation type reaction may be employed in the practice of this invention. Typical examples of suitable aldehydes and ketones include methyl ethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl hexyl ketone, butyl aldehyde and benzaldehyde.

The amine 0r amine precursors that are useful in carrying out reactions of the type contemplated by the present invention are any of the primary amines or amine precursors that will produce primary amines of the type normally employed in a conventional reductive alkylation reaction. Typical examples of suitable amines or amine precursors include aniline, para-nitrodiphenylamine, paraaminodiphenylamine, ortho-phenylenediamine and paranitroso-diphenylamine.

The amount of acid to be used in the two-component and three-component systems will vary somewhat, depending upon the particular reductive alkylation reaction in which the catalyst is to be employed, the sulfur-containing modifier used to modify the catalyst (if a threecomponent system is used) and the acids. However, it will in general be found that from 0.005 to 0.100 gram molecular weight of the acid should be employed per grams of nickel in the metallic catalyst.

The amount of sulfur-containing material that should be used to modify the nickel catalyst will also vary somewhat, depending upon the particular reductive alkylation reaction in which the catalyst is to be employed, the sulfur-containing modifier used to modify the catalyst and the acid. However, in general it has been found from about 0.05 to about 8.0 grams of contained sulfur should be employed per 100 grams of nickel in the metallic catalyst. A specific range is from 0.10 to 4.0 grams of contained sulfur per 100 grams of nickel.

The nickel catalyst/sulfur-containing modifier (if a three-component system is used) and acid may be added to the reaction mixture separately, all together or in any combination and in any order. One way, but by no means the only way, in which such a physical mixture may be conveniently prepared, is by slurrying the nickel catalyst in a solvent and adding the acid (or acid and sulfur-containing modifier) dissolved in the same solvent, mixing and then removing the solvent. The reductive alkylation reaction is normally conducted at temperatures between 50 and 240 C. Since a reductive alkylation reaction employs hydrogen it is necessary to conduct the reaction under substantial pressure. Normal pressures employed generally range from 250 to 2000 pounds per square inch, but in some cases may be substantially higher in the range of 4000 to 5000 pounds per square inch.

In order to most effectively catalyze a reductive alkylation reaction the catalytic systems of this invention are employed in an amount from 0.10 to 8 grams, based on the weight of contained nickel, per mol of primary amine in the reaction mixture.

In carrying out a reductive alkylation reaction wherein the catalytic systems of this invention are conveniently employed, the amine, nitro or nitroso compound is charged into a suitable reactor with an aldehyde or ketone that is to be employed as the alkylating agent and a catalytic system as has been described above. The aldehyde or ketone alkylating agent is normally employed in excess and acts as a solvent [for the reactants and thus alleviates the necessity of other solvent diluents being employed in the reaction. Other solvent diluents such as ethyl alcohol, isopropyl alcohol, benzene and toluene may be used if the aldehyde or ketone alkylating agent is not employed in an excess amount suflicient to act as a solvent for the reactants. The mixture is heated to a reaction temperature in the range of between 50 and 240 C. and hydrogen under pressure of from 250 to 2000 pounds per square inch is then introduced to the reaction vessel. The reaction is permitted to proceed for a period of time sufiicient to obtain conversion of the reactants to the N- alkyl substituted amine. The pressure on the reaction vessel is then released and the product is recovered by distilling oil the volatile materials. The employment of the catalytic systems of this invention results in high yields of the reductively alkylated product. The employment of the three-component catalytic system of this invention enables the reaction to be conducted at comparatively high temperatures where it proceeds readily without any significant conversion of the aldehyde or ketone alkylating agent to its corresponding alcohol. Reductive alkylation reactions of the type described may be carried out on either a batch or continuous basis.

The preparation of the catalytic systems of this invention and their use in reductive alkylation reactions are illustrated by the following examples, which should be considered representative rather than restrictive of the scope of the invention.

Example 1 is a control reaction using only a nickel catalyst. Examples 2 through 13 illustrate reactions using the two-component system.

EXAMPLE 1 Into a one liter autoclave equipped with a stirrer were charged 138 grams of distilled para-aminodiphenylamine, 300 grams of methyl isobutyl ketone and two grams of a 63 percent nickel-on-kieselguhr catalyst. The mixture was reacted for four hours at 165 C. under hydrogen at 750 to 1000 pounds per square inch pressure. The resulting product was then removed [from the autoclave and filtered. It was then distilled to 200 C. pot temperature at to 25 millimeters of mercury. Analysis of volatiles and product was conducted by gas chromatography. The volatiles showed 10.0 percent of the original ketones charged had been reduced to the corresponding alcohol. Analysis of the product showed a 75.5 percent yield of N-4-methyl-2-pentyl-N-phenyl-para-phenylenediamine.

Examples 2 to 13 were run in the same manner as Example 1 with the exception that various acids were used in combination with the nickel catalyst.

EXAMPLES 2 TO 13 Grams Percent of acid per ketone Ex. gram Percent reduced N 0. Acid catalyst Solution yield to alcohol 0.0088 Ethanol 77. 3 10. 9

0.0115 Ethanol 90. 2 4. 7

0.0070 Water 90. 3 3. 1

Indicates absolute ethyl alcohol in the above table and in any subsequent table in the specification.

The above data indicate that the presence of an acid improved the percent yield in each case. The oxalic acid, toluene sulfonic acid and sulfuric acid in addition reduced the amount of ketone that was reduced to the alcohol. This was particularly true where sulfuric acid was used.

Example 14 is a control reaction using only a nickel catalyst. Examples 15 through 66 were run in the same manner as Example 14 with the exception that the odd numbered examples were run using various sulfur-containing compounds in combination with the nickel catalyst while the even numbered examples were run using both sulfur-containing compounds and acids in combination with the nickel catalyst. The odd numbered Examples 15 through illustrate reactions using two-component systems disclosed in U.S. Pat. No. 3,366,684 issued Jan. 30, 1968. The even numbered Examples 16 through 66 illustrate reactions using three-component catalyst systems within the practice of the present invention.

EXAMPLE l4 Into a one liter autoclave equipped with stirrer were charged 138 grams of distilled para-amino diphenylamine, 300 grams of methyl isobutyl ketone and two grams of a 63 percent nickel-on-kieselguhr catalyst. This reaction was run for four hours at 165 C. under hydrogen at 750 to 1000 pounds per square inch pressure. The resulting product was then removed from the autoclave and filtered. It was then distilled to 205 C. pot temperature at 20 millimeters of mercury. Analysis of volatiles and product was conducted by gas chromatography. The volatiles showed 26.6 percent of the original ketones charged had been reduced to the corresponding alcohol. Analysis of the product showed a 57. 8 percent yield of N-4-methyl-2-pentyl-N-phenyl-para-phenylenediamine.

EXAMPLES 15 THROUGH 66 Combinations of 63 percent nickel-on-kieselguhr catalyst and various sulfur-containing modifiers were evaluated in the production of N-4-methyl-2-pentyl-N- phenyl-para-phenylenediamine both in the absence and in the presence of an acid, toluene sulfonic acid, using the same concentration of reactants and nickel catalyst and the same reaction conditions as described in Example 14. The sulfur-containing modifiers were added to the reaction mixture either as a solution or as a solid as indicated in column 2 of the following table wherein the efiectiveness of various catalyst systems is summarized. The toluene sulfonic acid was added in absolute ethanol.

Acid at- Grams toluene Grams Grams sulfouio modifier sulfur acid per Meltin Solid or per gram per gram gram point, Percent Ex. N o. Sulfur-containing modifier solution catalyst catalyst catalyst yield 1 15- Thiodipropionic acid Ethanol..- 0 0258 0.0047 35-44 81. 7 l6- do do .0268 0.0047 48-51 17. Xylene monosulfide MethanoL. 0 0331 0.0044 43-47 93. 8 18 do o. 0. 0331 0. 0044 45-48 100 19 Thioanisole do 0. 0180 0. 0047 43-48 93. 8

TABLE Continued Acid at Grams toluene Grams Grams sultonic q 1 1 inodi tier sulfur acid per Melting 1. c 1( 01' 101" ram 01 ram ram oint Per 11 Ex. No. Sulfur-containing modifier solution catz ilyst cat ftlyst, 03115113 80 p C yi e l d 20 .do "do..." 0. 0150 0.0047 41-45 100 1. 'll11od1p1op10n1tnle 0. 0206 0. 0047 44-48 07. 4 2?. .d 0. 0200 0. 0047 47-50 98. 8 23 Benzoth 0. 0200 43-48 02. 24 0.0200 0.0047 45-50 08.3 Mereaptobenzotl ole 0. 0240 0.0046 77. 5 20".. d0 0.0240 0.0046 45-49 07.9 D1-tcrt.-butylsulfide 0.0211 0. 0046 42-48 97. 3 d0 0. 0211 0. 0046 -50 97. 8 Benzotlnazole monosulfide- 0.0290 0. 0047 40-48 83. 0 0. 0290 0. 0047 44-48 97. 0 0. 0284 0. 0048 44-48 94. 5 0. 0284 0. 0048 44-49 96. 7 D1n1ethyl sulioxide 0. 0113 0.0046 46-50 94. 1 0 0.0113 0.0046 47-50 96.6 Tetramethyl thiuram monosulfide 0. 0150 0.0034 79. 0 .do 0. 0150 0.0034 41-47 95. 4 0. 0138 0. 0138 42-48 92. 4 0. 0138 0. 0138 -49 95. 3 0. 0582 0. 0046 38-47 36. O 0. 0582 0. 0040 42-48 94. 9 Beta-mercapto propionic ac1d 0.0154 0. 0047 40-47 93. 5 do 0. 0154 0. 0047 44-48 94, 8 43 Dithiodibenzoie aeid r 0- 0410 0- 0 43 1. l 44 do 0. 0410 0. 0043 47-50 04. 5 5. Tetramethyl thiuram disulfide 0. 0179 0. 0046 38-46 89.2 46 d 0. 0179 0. 0040 43-48 04. 5 n-Butyl ulfoxide O. 0234 0- 0046 35-45 80. 7 do 0. 0234 0. 0046 40-47 94. 3 Thiobenzoic acid. 0. 0200 0. 0046 37-46 81. 5 d (1o 0.0200 0. 0046 93.9 110111133 Ethanol 0. 0110 0. 0047 38-46 84. 3 0.0110 0. 0047 44-40 02. 0 Ditliiobenzoie 1 0. 0110 01.5 Thiomaiic acid, 0.0109 0 0024 74. 5 0. 0100 0. 0024 40-47 01. 0 0. 0240 0. 0047 82. 4 do 0. 0240 0 0047 30 10 00. 0 methyl. 0. 0178 0. 0040 40-44 83. 8 do 0. 0178 0. 0040 4040 00. 5 Benzyl disulfide 0.0180 0. 00-17 39-45 84. 0 0. 0180 0. 0047 41-46 88. 5 0. 0108 0. 0040 37-45 83. 7 do 0. 0103 07 0046 40-46 87.5 sodium m 0.0110 0. 0045 61. 4 66 "do 0.0110 0. 0045 0. 0220 74. 6

1 N -4-methyl-2-pentyl-N'-phcnyl-para-phenylencdiamine.

The yield data from the above table demonstrate that the addition of an acid to nickel catalyst/sulfur-containing modifier catalytic systems increases the percent tion of 0.0047 gram of sulfur per gram of catalyst. The toleune sulfonic acid was added in absolute ethanol, in a concentration of 0.0229 gram per gram of catalyst.

Melting Percent Ex. No. Alkylation system Catalytic system point, C. yield 184 grams p-arninodiphenylamine and 288 grams 2-octan0ne Nickel/modifier 100 184 grams p-aminodiphenylamine and 288 grams methyl ethyl ketonc- Nickel/modifier 48-51 100 .do Nickcl/modifier/acid 50-52 99.0

.do. Nickel/modifier. 48-51 98. 4

. 93 grams aniline and 400 g Nickel/modifier. 46. 3

54 grams p-phenylenediamine and 400 grams 2-oetanone. Nickel/modifier 88. 6

do Nickel/modifier 92.3

77 175 grams p-nitrodiphenylamine and 295 grams methyl ethyl ketone Nickel/modifier 94.0

78 do Nickel/modifier/acid. 96. 1

1 Run at 140 C.

yield in reductive alkylation reactions. The data also reveal that the melting point ranges were narrowed by using an acid, thereby indicating that the alkylation products possessed a high degree of purity.

EXAMPLES 67 THROUGH 78 The percent yield data in the above table reveal that the catalytic system of the present invention enhances the yield in various types of alkylation systems. Naturally in the cases where the percent yield is near theoretical it is impossible for the addition of an acid to substantially increase the percent yield. One of the advantages in using an acid in such systems is that it will allow the use of lower alkylation temperatures to obtain close to theoretical yields. Another advantage is that faster reaction rates for a given reaction temperature may be obtained. An indication of such an effect is demonstrated by the percent yield data in Examples 69, 70, 71 and 72. In the latter two examples the alkylation reaction was run at reduced temperature of C. instead of C. and yet close to theoretical yields Were obtained.

EXAMPLES 79 THROUGH 84 Various acids were evaluated in the production of N-4- methyl-2-pentyl-N-phenyl-para-phenylenediamine using a three-component catalytic system and the same experimental reactants and conditions as described in Example 14. Tliiodipropionic acid dissolved in absolute ethanol was 10 a sulfur-containing material selected from the group consisting of thiodipropionic acid and mercaptobenzothiazole, in a proportion to provide from 0.10 to 4.0 grams of contained sulfur per 100 grams of nickel and (c) from 0.005

used as the modifier in each case in a concentration of to 0.100 gram molecular weight of toluene sulfonic acid 0.0258 gram of modifier per gram of catalyst. The acids per 100 grams of nickel. were added in solution, the solvents being identified in 2. The process according to claim 1 wherein the N- column 3 of the following table. The effectiveness of the alkyl substituted amine is N-phenyl, N-4-methyl-2-pentylvarious acids is summarized in the following table. para-phenylenediamine, the ketone is methyl isobutyl ketone, and the sulfur-containing material is thiodipropionic Grams acld' acid e M If P t 3. The process according to claim 1 wherein the N- Ad d 801V 8 m gafi g p 3 5 6 g g alkyl substituted am ne 1s N-phenyl, N'-secondary heptylpara-phenylenedlamme, the ketone 1's methyl isoamyl keg??? 38: 3 tone, and the sulfur-containing material is thiodipropionic 48-50. 5 9s. 6 acid. e do 129 3% 4. The process according to claim 1 wherein the N'- leic Methanol 47-50 95.1 alkyl substituted amine is N-phenyl, N-4-methyl-2-pentylpara-phenylenediamine, the ketone is methyl isobutyl ke- The above data demonstrate that adds other than tgine, and the sulfur-containing material is mercaptobenzot azo e or anrc sulfonic acids ma be used in the ractice of this g y p 5. The process according to claim 1 wherein the N- invention.

alkyl substituted amine 1s N-phenyl, N-secondary-heptyl- EXAMPLES 85 THROUGH 88 para-phenylenediamine, the ketone is methyl isoamyl ke- Premodified catalytic systems were prepared by tone, and the sulfur-containing material is mercaptobenzoing the nickel catalyst in absolute ethanol and adding the thlazolesulfur-containing modifier and acid also dissolved in ab- In the @ductlve hlkylatloh P 'P 0f Produclhg all Solute ethanoL The Slurry was mixed W611 and dried in a N-alkyl substituted amine by reactmg a material selected vacuum oven. The free flowing solid premodified catalytic from the t} conslshhg of amine Compounds, hih'o C0111- systems were then used in place of the normal catalytic Pounds and 1113050 Q P with a material Selected systems using the same charge and conditions as described from th@ group conslstlhg aldehydes and ketones in the in Example 14 to produce N-4-methyl-2-pentyl-N'-phenyl- P i of y ge the Improvement wherein t e para-phenylenediamine. Both premodified nickel catalyst/ actlOIl 1S Conducted 1n the Presence of a catalytic amount sulfur-containing modifier and nickel catalyst/sulfur-conof a catalytic system comprising (a) a nickel catalyst taining modifier/ acid catalytic systems were used. The efa d (b) at least One acid selected from the group confectiveness of these premodified systems is compared in sisting of sulfuric acid, toluene sulfonic acid, oxalic acid, the following table. acetic acid, hydrochloric acid and oleic acid.

Acid at- Grams toluene Grams Grams sulionic modifier sulfur acid Melting Sulfur-containing per gram per gram per gram point, Percent Ex. No. er catalyst catalyst catalyst 6 0. yield 85 Thiodiproplonic acid-. 0 0258 0.00 46-50 93.9 do 0. 0258 o. 0047 0. 0229 48-51 97. 7 0. 0331 0. 0044 46-49 95. s 0. 0331 0. 0044 0. 0229 48-50 96. 7

The data in the above table demonstrate that the catalytic systems of this invention are also effective when prepared as premodified catalytic systems and that the addition of an acid increases the percent yield.

In summary, the co-pending United States application Ser. No. 426,408, now US. Pat. No. 3,366,684, has shown that the use of sulfur-containing materials with a nickel catalyst enhances the yields in reductive alkylation reactions without promoting undesirable side reactions. The present application demonstrates that the use of various acids in combination with nickel catalysts results in an improved yield in reductive alkylation reactions and in some cases reduces undesirable side reactants. In addition, the present application has shown that the use of various sulfur-containing materials in combination with the nickel catalyst/acid system results in even greater yields than are obtained with either the nickel catalyst/ sulfur-containing material or nickel catalyst/acid systems without promoting undesirable side reactions.

What is claimed is:

1. In the reductive alkylation process of producing an N-alkyl substituted amine by reacting p-aminodiphenylamine with a ketone selected from the group consisting of methyl isoamyl ketone and methyl isobutyl ketone in the presence of hydrogen, the improvement wherein the reaction is conducted in the presence of a catalytic amount of a catalytic system comprising (a) a nickel catalyst, (b)

7. The process according to claim 6 wherein the acid is selected from the group consisting of sulfuric acid. toluene sulfonic acid and oxalic acid.

8. The process according to claim 6 wherein the acid is sulfuric acid.

9. In the reductive alkylation process of producing an N-alkyl substituted amine by reacting a material selected from the group consisting of amine compounds, nitro compounds and nitroso compounds with a material selected from the group consisting of aldehydes and ketones in the presence of hydrogen, the improvement wherein the reaction is conducted in the presence of a catalytic amount of a catalytic system comprising (a) a nickel catalyst and (b) at least one sulfur-free acid.

References Cited UNITED STATES PATENTS 3,219,704 1/ 1965 Wilder et a1 260-576 LEWIS GOT-TS, Primary Examiner R. L. RAYMOND, Assistant Examiner US. Cl. X.R.

252430, 434, 436, 439; 260-4563 D, 570.9, 583 R, 585 C 

